Compressors are used to compress gases of all types, and in particular to compress air for various technical applications. For example, compressors are required to provide compressed air for operating pneumatic brake systems in motor vehicles and rail vehicles. In motor vehicles, the compressors are normally driven by the internal combustion engine which is provided to drive the vehicle. Where necessary, a secondary drive independent of the internal combustion engine may be provided for the compressor.
DE 198 48 217 A1 describes for example a gas compressor with an additional compression chamber. In order to minimize the power consumption of the gas compressor in unloaded running, i.e. when there is little demand for compressed air by the compressed air system, the cylinder chamber is enlarged by the controlled connection of a dead space volume by means of a displaceable and/or swivelable lamella, and in this way the mechanical drive power of the compressor is reduced in unloaded running.
In multi-cylinder compressors with pairs of pistons oscillating in opposition, it is also known to connect in each case two cylinder chambers together via a bypass channel in unloaded running, so that the compressed air is conveyed only to and fro between the cylinders, with a significant reduction in drive power. To achieve this objective, on unloaded running of the compressor, at least one bypass channel is opened at least partially by a suitable operating position of the lamellas set via actuators.